The first dinosaurs appeared about 235 million years ago (million years ago), in the Triassic period (from -251 to -201 million years ago) and survived until the fall of the asteroid Chicxulub, which caused their extinction – except for birds – at the end of the Cretaceous period. 66 million years ago.
A global and lasting success, as they have occupied virtually every terrestrial ecological niche and have taken on a wide variety of sizes and shapes. Part of this success is no doubt due to the variety of feeding behavior of the most primitive dinosaurs. According to a new study by the University of Birmingham (UK), another part of this success will be climate related.
At the end of the Triassic, dinosaurs and especially the first sauropods, which were much more modest than their descendants, giant herbivorous tetrapods such as diplodocus, were confined to small ecological niches, in low latitudes and in relatively warm zones. Previously, scientists believed that such a limited distribution is associated with competition with other animals that lived in the same period and reached large sizes. Among them are large etosaurs, similar to huge armored armadillos, no less impressive rauisuchians or therapsids, distant relatives of mammals, such as Lystrosaurus.
To better understand the interactions between these animals and the role of climate in the early history of the dinosaurs, the researchers used computer resources to model environmental conditions (temperature and rainfall) and compared them to the distribution of sauropods, data obtained by compiling a fossil database. It can be seen from this work that sauropods and sauropod-like animals, with their long tails, long necks and small heads, made great strides in a turbulent period of evolution.
Growth during a crisis
According to a study published in the journal Current Biology, it was climate variations that limited the emergence of sauropodomorphs, not competition with other large animals. But the end-Triassic crisis, probably triggered by intense volcanism triggered by the fragmentation of the Pangea supercontinent, changed the situation.
The average temperature rose due to the massive release of carbon dioxide and created much more favorable conditions for sauropods, which were able to expand their habitats. They also took advantage of the disappearance of other large vertebrates to fill the vacated ecological niches.
But even after this crisis, during the Jurassic, when they reached gigantic size, sauropods continued to stay in the hottest regions and carefully avoided the coldest places, unlike other groups such as hadrosaurs or some theropods that reached Alaska.